Fluid and Electrolyte Imbalance Lecture 3 4/24/2017

Acid Base Disturbance Plasma pH is an indicator of hydrogen ions concentration The increase in hydrogen in the blood make it acid while the lower hydrogen make it alkaline Normal plasma pH is 7.35-7.45 Lower pH means more acidity There is 3 important factors that control the pH of blood hydrogen ion H+, bicarbonate ions HCO3- and carbon dioxide CO2. H+ , HCO3- and CO2 are routinely measured in Arterial Blood Gas sample (ABG) The more HCO3- in the blood the more the alkalinity( normal value 22-26mEq/L) The more CO2 the more the acidity (normal value 35-45mmHg) 4/24/2017

Kidney and lung has the primary role in maintaining pH in the blood Kidney is responsible for the 24 hrs regulation of pH while the lung act mainly in the emergency situation Kidney regulate pH directly through bicarbonate and hydrogen ions . When the blood is acidic the kidney produce more bicarbonate and increase excretion of hydrogen ions . The opposite happens in case of alkalosis The lung helps in mainatinence of pH through CO2 control When the blood is acidic the lung increase the rate and depth of breathing which lead to wash off CO2 . When the blood is alkaline the lung decrease the rate and depth of breathing which entails more CO2 retintion in the blood Change in bicarbonate concentration in the blood reflect a metabolic disorder while the change in CO2 reflects a respiratory disorder . Change in both reflect mixed metabolic and respira.tory disorder 4/24/2017

Metabolic Acidosis A clinical disturbance that is characterized by low pH ( less than 7.35) low bicarbonate ( less than 22mEq/L and low hydrogen concentration. Clinical manifestations Increase rate and depth of breathing Peripheral vasodilation which lead to hypotension Decrease cardiac out put Neurologic sign such as headache confusion Causes: renal failure, loss of bicarbonate as in diarrhea, vomiting , lower intestinal fistula , excessive administration of chloride, hyperkalemia 4/24/2017

Metabolic Acidosis Medical management Adminsiter bicarbonate when pH below 7.1 Ringer lactate ( sodium lactate): metabolized into sodium bicarbonate inside the body correct hyperkalemia: Potassium move from inside the cell to the blood in exchange for hydrogen ions which increase acidity of the blood. 4/24/2017

Metabolic Alkalosis Clinical disturbance characterized by high pH ( higher than 7.45) and high bicarbonate (higher than 26mEq/L) Causes The most common cause is vomiting or nasogastric tube suction ( gastric secretion is pH is 1to3 and rich in hydrogen and chloride). Condition of hypokalemia 4/24/2017

Metabolic Alkalosis Clinical manifestations Usually related to decrease calcium ionization( calcium need acid environment to be chemically active) . Symptoms of hypocalcaemia develop such as tingling of fingers, respiratory depression Management Administration of chloride( increase bicarbonate excretion) Administer potassium in case of hypokalemia 4/24/2017

Respiratory acidosis A clinical disturbance charcterized by low pH( less than 7.35), and CO2 higher than 45mmHg. Causes All condition that increase CO2 in the blood such as respiratory diseases atelectasis, pneumonia…..) 4/24/2017

Respiratory acidosis Clinical manifestations Increase rate and depth of breathing Signs of vasodilation in brain and peripheral as a result of increase CO2 such as increase in intracranial pressure (ICP) Cardiac arrhythmia Hyperkalemia ( potassium increase as exchange with hydrogen ions) Medical management Manage respiratory disease, improve oxygenation 4/24/2017

Respiratory alkalosis Clinical disturbance characterized by high pH greater than 7.45 and CO2 less than 35mmHg Causes Main cause is Hyperventilation which cause excessive blow off ( wash off ) for CO2 Other causes include salicylate toxicity ( aspirin) Clinical manifestations Signs of decrease cerebral blood flow such as inability to concentrate, cardiac arrhythmia 4/24/2017

Respiratory alkalosis Medical management Treatment of the underlying cause 4/24/2017